Apparatus for purifying liquefied gases



July 1934' w. F. MOELLER 1,967,718

APPARATUS FOR PURIFYING LIQUEFIED GASES Original Filed April 25, 1932 2 Sheets-Sheet 1 INVENTOR mqmum/L July 24, 1934. w F. MOELLER 1,967,718

APPARATUS FOR PURIFYING LIQUEFIED GASES Original Filed April 23, 1932 2 Sheets-Sheet 2 ATTORN Y5 UNITED STATES PATENT OFFICE APPARATUS FOR PURIFYING LIQUEFIED GASES Walter F. Moeller, Mount Lebanon, Pa., assignor,

by mesne assignments, to The Linde Air Products Company, New York, N. Y., a corporation of Ohio Original application April 23, 1932, Serial No. 7 607,032. Divided and this application May 22,

1933, Serial No. 672,191

6 Claims. (Cl. 202158) This invention relates to a process and appafor carrying out the process of the present ratus for purifying liquefied gases, for example, invention;' and liquid oxygen, nitrogen, and the like, which are Fig. 2 is a view mainly in vertical section produced in a manufacturing cycle, where they showing a gas production apparatus incorpo 5 are generally contaminated with undesirable rating purifying apparatus arranged for the 55 impurities and has for its main object an impractice of the present invention. proved procedure whereby such impurities are In the commercial production of a purified readily and expeditiously removed. liquefied gas from which undesirable impurities lylore specifically, the invention relates to the are substantially completely removed, the puriprovision of suitable steps for concentrating unfi n may e accompli h d with the Xp n- 60 desired impurities occurring in the production i re of relat v ly li le ner y y taking the of liquefied gases of the character indicated in gas m a i e qu d phase d treating it a manner in the cycle of production such that y the p of Partial evaporation to produce the impurities may be separated readily by metWO p s a d t en p at the P chanlcal means, whereby a gas product i fithis process being generically set forth in the o5 nally obtained in the liquid phase from which appending pp io fil d in h n m f substantially all impurities afe practically com- Lawrence J Bowditch O April 1932, Serial pletely removed, I No. 607,074, where it is proposed to remove Another object is to produce a liquefied gas i those impurities which occur in relatively small a purified condition with an expenditure of a amounts in liq d ga uch a liquid r, 70 relatively small amount of additional energy and Oxygen, Carbon d n the like, th e at relatively little additional cost, tration being such that they do not materially still another object is to separate the desired change the il p i f the liquefied gas, liquefied gas from the undesired impurity by but are otherwise objectionable and impair the 25 the step either of partial evaporation or partial Commercial q t es o t e gas p od 75 condensation and thereafter causing the gas e e a e ce t type of impurities 00mmaterial to revert to the liquid phasewith an mohly i p a d W the gas material, on expenditure of a relatively small amount of account of the source from which the gas is obenergy. tained and on account of the manufacturing Other objects of the invention will in part be steps commonly employed, which are less volaso obvious and will in part appear hereinafter. tile t an the as e al, ehave melting This application is a division of my original p in s m rial y ove the boiling p in f he application Serial No. 607,032, filed April 23, s m rial. To ac mpli h the removal of 1932. such impurities, it is proposed to bring the gas The invention accordingly com rises the sevm er l con inin the un ired impuri y in so eral steps and the relation of one or more of a single phase by the step of fractional evaps h steps with respect to each of th thers, oration or condensation under conditions of a d th apparatus embodying features of m temperature and pressure where the vapor presstruction, combinations of elements and aru e o t p y is of a negligible va ue.

rangement of parts which are ada tetd to effect Two phas a us p du d that m y be s psuch steps, all as exemplified in the following arated physically while the impurities remain in detailed disclosure, and the scope of the applit e l q 0 Solid p Here it is p op d o cation of which will be indicated in the claims. Practice these steps in c nj nction with a step For a fuller understanding of the nature and of condensation, in order finally to obtain a 45 objects of the invention, reference should be had liquefied gas such as liquid oxygen in substanto the following detailed description taken in tially pure condition, this step being preferably connection with the accompanying drawings, practiced so as to accomplish the condensation in which: I by the utilization of a by-product from another Fig. 1 is a view mainlyv in vertical cross secportion of the cycle of production.

50 tiOn Showing a ple form of apparatus adapted Referring now to the drawings, and particularly to Fig. 1, A denotes generally apart of the apparatus into which the gas material in liquid phase that is to be purified is passed and caused to evaporate partially by the application of heat, while B denotes a second part serving to condense the vapor produced in part A, which is conducted thereto and recondensed by bringing it into thermal contact with a fluid of lower temperature than the condensing temperature of the gasimaterial being purified.

The vaporizing portion of part A consists of a vessel 10 having an inlet conduit 11 for the liquefied gas, an outlet conduit 12 for the vapor, and a drain conduit 13 with a control valve 13. In the lower part of vessel 10 is a suitable heating means, for example a coil 14 provided with inlet and outlet connections adapted to be supplied with a heating agent. This agent may be any convenient vehicle that will pass without difiiculty at the low operating temperatures here employed, for example, compressed air. In the preferred form of the apparatus, the vapor outlet conduit 12 surrounds the inlet conduit 11 in order to effect heat exchange and separation of the liquid from the gas phase; the vapor thus separated being led. from the top.of the evaporating vessel 10 to the condensed The condenser shown in connection with part B consists of an upper header 15 and a lower header 16 connected by condenser tubes 17. The conduit 12 is here shown as discharging the vapor to be condensed into the upper header 15, while a conduit 18 is connected to the lower header to withdraw the reliquefied gas. The condenser is disposed within a chamber 19 having inlet and outlet conduits 20' and 21, respectively, for the purpose of circulating a cooling medium, for example, liquefied oxygen, or a cold gaseous material that may be a by-product drawn from another part of the manufacturing cycle; the cooling medium carrying away the heat from the condenser so that re-liquefaction is readily accomplished in the condenser.

The operation of the process in the apparatus described is as follows: In previous portions of the manufacturing cycle, certain impurities are not entirely removed and hence appear, though in relatively small quantities in the liquefied gas which enters *the vaporizer A through conduit 11. The flow of liquid into the vaporizer and the rate at which heat is supplied by the heating fluid passing through the coil 14 are adjusted by the operator to maintain a certain liquid level in the evaporator. The supply of heat causes evaporation of the liquid to occur, but the impurities, which are solid or in solution have a negligible vapor pressure at the temperature of the evaporating liquid, and remain in the liquid and areconcentrated at this point in the cycle. The concentrated impurities may be drawn ofi at will through conduit 13 by means of valve 13, together with some of the liquefied gas. I

The vapor is conducted through conduit 12 into the condenser at its upper header 15 whence it passes into the tubes 17 and is condensed because it loses heat through the tube walls to the fluid of lower temperature surrounding the tubes. The liquefied gas collects in the lower header 16 from which it is withdrawn through conduit 18 in a purified state.

In the modified form of apparatus shown in Fig. 2, a heat interchanger for the manufacture of liquefied oxygen is modified and arranged to separate out the impurities which have relatively high boiling points and are in general inflammable, and then recondense the purified oxygen in order to supply it in the liquid phase. Here a conduit 25 provided with an expansion valve 26 is arranged to supply compressed air drawn from a suitable high pressure source to the rectifying column shown generally at 27. This rectifying column is provided with a kettle or evaporator 28 at its. lower end and a condenser 29 at its upper end. A conduit 30 provided with an expansion valve 31 and distributor 32 is arranged to draw liquid from the evaporator 28 and'to discharge it into the upv per portion of a second rectifying column 33 disposed above the column 27 and arranged to be in heat exchanging relation with the condenser 29. Each of these columns is provided with suitable counter-current contact cooling means, for example, a series of perforated trays,

as shown at 27 in the column 27 and at 33' in the column 33. The evaporator 28 associated with the column 27 is provided with suitable heating means, for example, a heating coil as.

shown at 28'.

Within the column 2'7 isa tray 27" arranged to collect the condensate which drips from the condenser 29 and to convey the same to a conduit 34 having a controlling valve 35 and a distributor 36 discharging into the top of the column 33, the distributor 36 being preferably disposed above the distributor 32. From the top of the condenser 29 is a gas withdrawal'conduit 3'? which is arranged for withdrawing non-corrdensible vapors, while a liquid withdrawal conduit 38 is arranged to withdraw liquid from the base of the column 33 from about the condenser 29.

From this arrangement, it isseen that the compressed air'introduced into the column- 2'1 is liquefied by the passage through the expansion valve 26 and through the trays 27';-the

liquid collecting in the vaporator 28. Gas or vapor rising through the column 27 passes into the condenser 29 where the less volatile portion is recondensed to produce a'refiux in the column 27. Liquid nitrogen collects in the tray 27'-, whereas the liquid in the evaporator 28 comprises a relatively large percentage of liquid oxygen. Any non-condensible vapor that is more volatile than liquid nitrogen or oxygen is withdrawn through the conduit 37; Liquefied gas comprising mainly liquid oxygen and the impurities of relatively high melting point are withdrawn through the conduit 30 and introduced into the column 33 through the distributor 32.

In orderqto effect the final stage of purification, in accordance with the present invention, a second condenser shown generally at 4,0 is incorporated at a convenientpoint in the column 33. This condenser comprises upper and lower portions 41 and 42, connected by an intermediate portion 43. One or more passages or fiues 44 are associated with the condenser in order to establish communication between the space above the condenser with the space below; a

chamber for this condenser being preferably provided in the column by means of a partition 45 disposed transversely in the column below the condenser and a second partition 46, which The partition 46 is provided with one or more passages 47 that permits communication with the flues 44 so as to establish communication in the column 33 for the space on the two sides of the condenser chamber containing condenser 40. The partition 46 is also provided with one or more liquid drains 48 which allow liquid to drain from the partition into the chamber about the condenser 40. Gaseous oxygen to be recondensed and which has been evaporated by the condenser 29 is led from a point near the lower end of the column 33 from the chamber about the condenser 29 by means of a conduit 50 and passed into the portion 41 of condenser 40. Here liquid oxygen collects in a purified state and is withdrawn from the lower portion 42 through a conduit 51.

The operation of this latter form of apparatus r's seen to be as follows: The compressed air from which oxygen in the liquid phase and in a purified state is desired to be obtained is introduced into the rectifying column 27 either with or Without previous partial purification. This is then passed through the conduit 30, the expansion valve 31 and the distributor 32 into the column 33, where the cooled oxygen condenses out and passes down through the trays 33' and through the drain 48 into the chamber about the condenser 40. When the desired liquid level is attained in this chamber, the cooled liquid overflows through the by-pass 44 into the lower portion of the column 33 over the trays 33" and finally collects in the chamber about the condenser 29. Here the heat absorbed from the condenser 29 in effecting refrigeration for the column 27 vaporizes a portion of the liquid which is now a high concentrate of liquid oxygen contaminated with the impurities of relatively high melting point. The oxygen vaporized in this chamber is substantially pure oxygen gas which is withdrawn through the conduit 50 and passed into the condenser 41, where it is recondensed by the heat abstracted by the liquid in the chamber about the condenser 41. Thus it is seen that liquefied oxygen in the purified state desired collects in the portion 42 and is withdrawn by the conduit 51.

The liquid which collects in the chamber about the condenser 41 is seen to comprise a mixture of oxygen and nitrogen in the liquid phases, together with any substances that may be present either as solids or in solution. The vaporization which takes place in this chamber is of a fractional nature, the more volatile nitrogen being boiled oil and passed up through the fiues 47 into the upper portion of the column 33. This liquid nitrogen is seen to be supplied to the column ma nly from the conduit 34; thus the cooling of the condenser 41 is seen to be accomplished by means of a cooling agent that is withdrawn from another portion of the cycle of production. The vaporized nitrogen is seen to pass from the top of the column 33 in the usual manner.

The agents here used for heating the liquid in the evaporators and for extracting heat from the vapor in the condensers, in order to conserve energy, are thus with advantage both taken from some other portions of the cycle of production, and since no change has occurred therein other than a change in the quantity of absorbed heat, they may be returned, if desired, to the cycle substantially without loss.

Since certain changes in carrying out the above process and in the constructions set forth, which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In apparatus for the commercial production of liquid oxygen free from undesired impurit'es, the combination with a rectification column having an inlet by which gas material in the liquid phase is introduced and an evaporator adjacent the lower end, of counter-current gas and liquid contactmeans in said column between said inlet and said evaporator, said rectificaton column being provided with a chamber to which a refrigerating agent is admitted from another part of the system, a condenser disposed in said chamber and spaced from the walls thereof, means for supplying a gas fraction drawn from said evaporator to said condenser, and means for withdrawing the con densation product directly from said condenser to a point on the exterior of said column.

2. In apparatus for the commercial production of liquid oxygen free from undesired impurities,

the combination with a rectification column having an inlet by which gas material substantially in the liquid phase is introduced, an evaporator at its lower end and a condenser at its upper end, of a second rectification column having its lower end connected to be in heat exchanging relation with the fiuid in said con denser, a connection leading from said first rectification column and discharging into the second near the upper end thereof, an auxiliary condenser located within said second rectification column exposed to a refrigerating agent and spaced from the column walls, a connection arranged to supply a gas fraction withdrawn from said second rectification column to said auxiliary condenser which is distilled off by the heat of said first condenser, and a withdrawal connection for withdrawing the condensate from said auxiliary condenser.

3. In apparatus for the commercial production of liquid oxygen free from undesired impurities, the combination with a rectification column having an inlet by which gas material substantially in the liquid phase is introduced, an evaporator at its lower end and a condenser at its upper end, of a second rectification column having its lower end connected to be in heat exchanging relation with said condenser and a connection for receiving liquid at its upper end which is withdrawn from said evaporator, said second rectification column being formed with a chamber at a point intermediately of its ends, a second condenser disposed within and spaced from the walls of said chamber, means for supplying a refrigerating agent to said chamber, means for supplying a gas fraction distilled from said second rectification column to said second condenser whereby a purified liquefied gas is collected in said second condenser, and means for directly withdrawing the collected condensate from said second condenser.

4. In apparatus for the commercial production of liquid oxygen free from undesired impurities, the combination with a rectification column having an inlet by which gas material substantially in the liquid phase is introduced, an

evaporator at its lower end and a condenser at its upper end, of a second rectification column superposed above the first column and having its lower end in heat exchanging relation with said condenser and a connection for receiving liquid at its upper end which is withdrawn from said evaporator, said second rectification column being formed with a chamber at a point intermediately of its ends, a second condenser disposed within and spaced from the walls of said chamber, means for supplying a refrigerating agent to said chamber withdrawn from another portion of the apparatus, means for supplying a gas fraction to said second condenser distilled from said second rectification column whereby the purified liquefied gas is collected in said condenser, and means for directly withdrawing the collected condensation product from said second condenser.

5. In apparatus for the commercial production of liquid oxygen free from undesired impurities, the combination with a rectification column having an inlet by which gas material in the liquid phase is introduced near the upper end and an evaporator adjacent the lower end, of countercurrent contact means in said column between said inlet and said evaporator, perforated partitions located so as to interrupt the regular occurrence of said counter-current contact means at an intermediate point and providing a chamber within said rectification column, a condenser disposed within and spaced from the walls of said chamber, the perforations in said partitions being arranged for admitting a refrigerating agent to said chamber, means for supplying a gas fraction drawn from said evaporator to said condenser, and means for withdrawing the condensation product from said condenser.

6. In apparatus for the commercial production of liquid oxygen free from undesired impurities, the combination with a rectification column having an inlet by which gas material in the liquid phase is introduced near the upper end and an evaporator adjacent the lower end, of countercurrent contact means in said column between said inlet and said evaporator, perforated partitions interrupting said counter-current contact means at an intermediate point to provide a chamber within said rectification column, a condenser within and spaced from the walls of said chamber, pipe connections for leading a gas fraction directly from said evaporator to said condenser, means for withdrawing the condensation product from said condenser, the perforations in said partitions admitting the passage of liquefied gas material drawn from an upper part of the column as the refrigerating agent to said chamber, and means for withdrawing said gas material when the refrigerating efiect is spent and returning the same to another part of said rectification column.

WALTER F. MOELLER. 

